This invention relates to a bottle closure for bottles having a circumferential bead around the bottle opening and which forms a downwardly directed external shoulder. The closure comprises a resilient sealing element slidably arranged in the hollow of a rigid retaining cap having a circular cross section and a side wall which is terminated at the top by a transverse top wall having a central aperture and which at the lower portion thereof is extended by means of a diverging skirt having an inwardly turned rounded flange. In its inactive position the sealing element will have a corresponding form but with substantially smaller axial dimension for sliding movement within the retaining cap between a lower resting position and an upper working position compressed around the opening of the bottle neck.
Such a bottle closure has been described and shown in U.S. Pat. No. 2,903,148.
The subject invention is directed to improvements over the above mentioned prior art which eliminate the various drawbacks in the known type of bottle closure. For instance, in the known bottle closure the internal contact surfaces between the slidable sealing element and the inner wall of the retaining cap must be impregnated with some sort of lubricating material to reduce frictional resistance to the movement of the sealing element between its two relative positions. Such lubricating material may be a silicone lubricant. However, these lubricating materials will be subjected to action from the gases or vapors contained in the liquid content of the bottle and the lubricating effect will disappear after a very short time. Furthermore, the bottle closures belonging to the art have proved to be ineffective in sealing when the bottles contain carbonated beverages. Also the sealing element in itself is subjected to structural deformations after a certain time, which again is very unfortunate for the sealing function and will lead to a very short lifespan for the bottle closure in question.
The subject invention has for its main purpose to eliminate said drawbacks in the prior art by providing a bottle closure having improved sealing characteristics and which furthermore is easy to operate, will have lower production costs and an extended lifespan compared with previously known constructions.
The invention meets the requirements by having a sealing element provided with an annular collar made from a friction reducing material such as polypropylene or similar material inert towards the actual gases and vapors. In accordance with a further feature of the invention the annular collar forms a portion of the external surface of the sealing element and is substantially the contact surface engaging the inner wall of the retaining cap. It is even a feature of the invention that the annular collar is made from a non-resilient material and has a skirt formed by downwardly directed flaps covering that portion of the sealing element which is subjected to deformation during movement from the resting position to the working position of the element.